Calculations (Yes, We Need Some, Sorry)

Welcome to the fourth day of Shawl Design for Beginners! Today we’re going to talk about shawl design calculations and how to overcome math phobia to get ready to calculate the basics of our new shawl design.

“I want my shawl to be X inches wide.”

How many rows to achieve this? How many stitches to cast on? Questions over questions! Let’s start at the beginning.

First Things First: Gauge

The very first thing we need to define is our knitting gauge. How many stitches and rows do we need using our chosen yarn and needles in our chosen pattern to achieve a certain width and height? The answer is your gauge, so start with knitting a swatch and find out how many stitches and rows you get in a certain width, like 4 by 4 inches (10 x 10 cm).

You can learn more about gauge in my following articles:

Shawl Design Calculations

The next step after finding out your gauge is to define the target length and width of your shawl. The numbers strongly depend on the chosen shawl shape, and our example will use the triangle knitted sideways we’re working on together.

We declared our desired width at the longer side of our example triangle shawl in the assignment of day one. Most of you chose a length of approximately 60 inches (150cm) for the longer side. Let’s have a look at an illustration of our shawl-to-be.

A triangle shawl worked sideways. The longer side labeled as “L” should be around 60 inches (150cm) long.

As soon as we chose a number for L (like the 60 inches in our example) and have a certain gauge to work with, both H (height) and W (width) are defined automatically. Don’t believe me? Well, mathematics does the trick.

Calculating Our Example Shawl

In our example shawl we chose L = 60 inches (150cm). In case you’re not interested in the details

Trigonometry tells us that our target width W for our example shawl, with increases every other row, is given by

 W = L  * sin(45°)  = L * 0.7 = 42 in (107 cm)

If in doubt, multiply your chosen length L by 0.7 to get you target width W.

Now we know our target width in inches (or centimeters), but how many stitches do we need in the end to achieve our target width? This is where gauge comes in.

We know how many stitches we need to achieve a width of 4 inches (10cm). Let’s assume we got a gauge of 5 stitches and 6 rows in 1 x 1 inches (2 stitches / 2.4 rows per cm). This means we need to knit 5 stitches to get a width of 1 inches (2 stitches for 1 cm). To get our number of total stitches at the upper side, where our shawl is W in (W cm) wide, we need to multiply our target width W by our number of stitches per inch (stitches per cm):

STS = W * STS / in (cm) = 42*5 = 210 sts

This means, as we’re increasing every other row, we need to knit 205 (=210-5) rows if we cast on 3 stitches in the very beginning to achieve our target width.

Let’s Sum Up

  1. Define your target length L.
  2. Get gauge.
  3. Calculate your target width W by multiplying L with 0.7.
  4. Multiply W with your number of stitches per inch (cm) – this is your number of stitches at the top end of the shawl.
  5. Divide the result of 4. minus your cast on stitches by two to get the number of total rows you need to work.

If you’re tired of just thinking about calculating anything might be the app for you – it calculates all these things for you automatically. Really! No fluff!

Any questions? If yes, make sure to leave a comment below!

Julia <3

12 thoughts on “Calculations (Yes, We Need Some, Sorry)

  • Hi Julia, thank you so much for sharing your knowledge!!! That is so great.
    There’s one thing i don’t understand in the calculations at Step 5.
    My gauge is 20st x 35,5 rows =10 cm
    My L is 200 cm so my W will be 140 cm (and so 280 st)
    My CO is 10 st. So at step 5 where you say: Divide the result of 4. minus your cast on stitches by two to get the number of total ROWS you need to work , I’ll get 280 minus 10 divided by 2 = 135 rows
    But 135 rows will be 38 cm. And when i calculate H by the formula a2 + b2 = c2 H will be 142,8 cm and that is 507 rows.
    So what do i do wrong? Or am i misreading something?
    Thank you. And keep on sharing!! 🙂
    Kind regards, Ana

  • Mary Whiteaker

    I am trying to make a triangle that Is 26 inches on 2 sides and 56 on the last side.
    Using size 15 knitting needles. Can you help? I can’t make it come out right
    Thank you

  • clicked on while reading end of blog, it read not available.

  • Judi R.

    Will your mathematics work for designing a “boomerang” shaped, or “crescent” shaped shawl?

  • sue B.

    Your tutorial is exactly what I was looking for! Thank you for your easy to follow mathematics. I very much look forward to learning from you.

  • Connie

    Hi – I need some help, please. I’m knitting prayer shawls for my church, and they’d like the shawls to be sized consistently. If I want to make one with #4 yarn, 10.5 needles, 30″ wide, how many stitches to I need to cast on?

    Thanks a bunch,

    • Julia

      Knit a swatch first please. Without, nobody can really tell!

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  • Venette Schafer

    This is not only my first shawl to try to design but my first to knit. I have started the pattern you assigned. I’m thinking that there is going to be more to it then what’s there so far??? There is no decreasing or anything about binding off. Well there be lace to the pattern?

  • Kathryn Morgan

    I’m so excited about designing and knitting my own shawl. I’ve never designed one before but knitted loads. I think my shawl should measure approx 160 cms on the longest edge as this seems to be the length of my arm span.

    I have chosen a 4ply yarn – I have 300g, approx 1050m in length. The one skein is black and the other variegated black, dark grey, med grey and light grey. I have in mind doing lace with the black and garter stitch stripes with the variegated. I am just struggling with which lace pattern to use. I”d really like something very simple but I’m not really a fan of anything too open. Perhaps you have some suggestions?

  • Sylvana

    Thank you for this step by step. It is very clear and the way you explained, it makes sense.

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